1. Field of the Invention
The present invention relates to electronic shift and throttle systems and, in particular, to increasing and decreasing engine throttle.
2. Description of the Related Art
Vehicles such as marine vessels are often provided with electronic shift and throttle systems. These systems typically allow an operator to control the shift and throttle functions of a propulsion unit using a control lever which is pivotally mounted on a control head. The control lever is moveable between a forward wide open throttle (forward WOT) position and a reverse wide open throttle (reverse WOT) position, through a neutral position. A controller reads the position of the control lever as the control lever moves through its operational range. The controller sends shift commands and throttle commands which drive a shift actuator and a throttle actuator based on the position of the control lever.
For example, U.S. Pat. No. 7,330,782 issued on Feb. 12, 2008 to Graham et al. and the full disclosure of which is incorporated herein by reference, discloses an electronic shift and throttle system in which a position sensor is used to sense the position of a control lever. The position sensor is electrically connected to an electronic control unit (ECU) and sends an electrical signal to the ECU. The ECU is able to determine the position of the control lever based on the voltage level of the electrical signal received from the position sensor. The ECU then determines the positions to which the output shafts of the shift actuator and the throttle actuator should be set.
Each of the output shafts is also coupled to a corresponding position sensor. Electrical signals sent by these position sensors may be used to determine the positions of the output shafts. This feedback may be used to govern the ECU. This is beneficial because variances and play between components used to link throttle actuators to throttles make it desirable to calibrate throttle controls. Calibrated throttle controls allow an operator to more accurately increase or decrease engine throttle in a marine vessel.